1. Field of the Invention
The invention relates generally to electrical enclosures and, more particularly to support assemblies for electrical enclosures.
2. Background Information
Electrical switching apparatus include, for example, circuit switching devices and circuit interrupters such as circuit breakers, contactors, motor starters, motor controllers and other load controllers.
Low voltage (e.g., without limitation, up to about 690 VAC; any suitable low voltage) circuit breakers, for example, which are used in power distribution systems, are commonly mounted, either alone or in combination with additional switchgear, within an electrical enclosure (e.g., without limitation, a load center; a switchgear cabinet). Typically, each circuit breaker is disposed within its own section of the electrical enclosure, referred to as a cell. Such circuit breakers can be relatively large and, therefore, are typically configured in a draw-out arrangement in which the circuit breaker is mounted on a movable frame or cassette that can be drawn out of the cell in order to, for example, gain access to the electrical terminals and bus work on the back side of the circuit breaker. Drawing the circuit breaker out of the housing assembly also provides access to the bus members, which are generally disposed behind the circuit breaker.
More specifically, the electrical enclosure contains current-carrying conductors, known as runbacks, which feed electrical power to, or carry electrical power from, the circuit breaker. The runbacks are contained by a support, which must be adequately designed with electrically insulating features to resist phase-to-phase contact or ground contact during normal operation of the circuit breaker. Known runback supports span the full width of the circuit breaker cell. Thus, when two circuit breakers are mounted side-by-side, either an elongated single-piece runback support is employed, which spans the full width of the electrical enclosure (e.g., across two cells that are arranged side-by-side), or two independent runback supports and an intermediate metal framework disposed between the circuit breakers and the two independent runback supports are required, wherein the intermediate metal framework supports one end of each of the runback supports, and the other end is supported by a corresponding wall or exterior framework of the electrical enclosure.
Both runback support designs suffer from a number of disadvantages. The single-piece runback support is relatively large, requiring a correspondingly large mold to make the support. This increases tool and part costs, and decreases the number of different circuit breaker configurations for which the single-piece runback support can be employed. It is also underutilized in the event only one circuit breaker is employed instead of two circuit breakers, in the aforementioned side-by-side configuration. Among the disadvantages of the intermediate metal framework and two independent runback supports, is the potential for unintentional grounding presented by the intermediate metal framework. Such framework also takes up valuable internal space within the electrical enclosure. Additionally, in the event only one circuit breaker is employed, a relatively large mold is needed to fill the empty space (e.g., cell) adjacent the single circuit breaker, in order to fill the empty cell of the electrical enclosure and thereby maintain the support across the width of the electrical enclosure.
A still further disadvantage is that known runbacks and runback supports require an excessive amount of hardware (e.g., without limitation, brackets, bolts, washers, nuts and combinations of bolts, washers and/or nuts) to secure the components of the assembly together. Typically, such hardware is electrically conductive and can encroach on minimum electrical clearance requirements (e.g., without limitation, “through-the-air” minimum clearance requirements, as defined herein; “across-the-surface” minimum clearance requirements, as defined herein), which are mandated by regulation.
There is, therefore, room for improvement in electrical enclosures and in support assemblies therefor.